I. Field of Invention
The present invention relates generally to a method for isolating insect pheromones. More particularly, the present invention relates to a method for purifying pheromone-binding proteins, and then using the purified proteins to capture insect pheromones.
II. Description of Related Art
Insects receive information from external chemical signals by means of receptors located primarily in the antenna. The dendrites of olfactory receptor neurons in the antenna typically are located in sensilla, thin hair-like structures which protrude from the antennal surface (Altner and Prillinger, 1980; Zacharuk, 1985). Receptor neurons appear to be specialized for particular substances, and each olfactory sensilla may contain dendrites from many different receptor neurons. The plasma membranes of the dendrites contain the olfactory receptor proteins (Hildebrand and Shepard, 1997; Krieger and Breer, 1999).
When activated by an odor or pheromone molecule, the receptors couple to G proteins, which in turn alter ion channel conductance in the receptor neuron membrane, mostly via an IP3 pathway (Breer et al., 1990), although a parallel cAMP pathway may also occur (Krieger et al., 1999). The receptor neurons form synapses with interneurons in the glomeruli of the antennal lobe of the brain (Hansson and Anton, 2000). Projection neurons carry the signals from the antennal lobe to the mushroom body, where synchronous firing is observed after odor detection (Laurent and Davidowitz, 1994). Olfactory information appears to be encoded in the synchronization. Neurons involved in decoding have been identified outside the mushroom body, forming synapses with the intrinsic neurons of the β lobe (McLeod et al., 1998). cAMP signaling pathways in the mushroom body are used for storage of olfactory memory (Skoulakis et al., 1993; Davis and Han, 1996), and short-term memory formation involves α-integrin (Grotewiel et al., 1998).
Pheromones are a major communication channel for insects. For instance, ants use pheromones to identify the colony, signal alarms, mark trails to food, attract workers to brood and to the queen, and bring males and females together for mating (Hölldobler and Wilson, 1990). Queen pheromones also may be involved in the maintenance of polygyny (multiple queen colonies) (Keller and Ross, 1998; Ross and Keller, 1998; Krieger and Ross, 2002) and in founding slave-making colonies (Mori et al., 2000). In addition, foraging, feeding, and defending the nest depend on detection of general odors and tastes and on detection of kairomones (signals from other species). Similarly, many other insects rely upon pheromones, often for similar types of communications.
The isolation and identification of various pheromones from insects is significant for a variety of reasons. For instance, these pheromones would assist in uncovering new basic information about the olfactory communication system and social behavior of social insects. Furthermore, knowledge of the pheromones would have direct application to management and control of various insect pests, including termites and fire ants. Unfortunately, pheromones are present in small quantities in natural sources, and may be difficult to isolate using conventional techniques. A need therefore exists for new methods of isolating pheromones.